ETO interacts with Bcl-6 in vivo. (A) 293T cells were transfected with HA-ETO, myc-Bcl-6 plasmid, or the respective empty vectors. Whole-cell lysates were immunoprecipitated with an ETO-N-terminal polyclonal antibody or normal rabbit serum (NRS) as a negative control and immunoblotted for myc to visualize the Bcl-6 ETO expression (upper panel) or for HA to verify ETO expression (lower panel). (B) Reciprocal immunoprecipitation in similarly transfected 293T cells in which control IgG, HA, or myc (to myc-Bcl-6) antibodies were used to pull down HA-ETO. (C) Whole-cell lysates from Raji cells (left) or Daudi cells (right) were subjected to immunoprecipitation of endogenous ETO with an N-terminal polyclonal antibody or rabbit serum control (NRS) and were subsequently immunoblotted for endogenous Bcl-6 with a mouse monoclonal antibody.